Support for more intelligent NUMA placement of guest VCPUs. Plus support in the cpupools subsystem for creating a pool per NUMA node.

libxl improvements

The libxl API is now stable.

The libxl featureset has been greatly expanded:

Long running operations can now be done asynchronously.

Improved event handling subsystem.

Remus compression (compression of memory image improves performance)

XenStored

Default to oxenstored when available. Oxenstored is faster, more scalable and more reliable than the C xenstored. In particular the transaction model in oxenstored does not involve taking a complete copy of the database and aborting on any (even non-conflicting) other change. For more detail on the design, implementation and a performance comparison see this paper.

Support for xenstored (C version only) in a stubdomain, improving scalability and security.

Support for upstream qemu

Used by default when required for PV guests (e.g. qdisk backend or VFB support)

Optional tech preview for use with HVM guests. Missing features:

PCI Passthrough.

Live Migration support.

Initial support for using OVMF UEFI firmware with HVM guests (requires upstream qemu)

Added libvchan interdomain communication library.

Xen

EFI (extensible Firmware Interface) support for hypervisor. Allows Xen to boot on machines which use EFI rather than a traditional BIOS

AMD OSVW (OS Visible Workarounds): Disables OS workarounds for hardware errata which are not necessary to workaround in guests because it is handled at the host level.

Early boot time CPU microcode patching. Xen can supplied with the microcode image by the bootloader (see the ucodecommand line option) and load it early rather than relying on the domain 0 kernel to supply it later.